It was first stated by J. Bristol Foster in 1964 in the journal Nature, in an article titled "The evolution of mammals on islands." In it, he studied 116 island species and compared them to their mainland varieties. He proposed that certain island creatures evolved into larger versions of themselves while others became smaller versions of themselves. For this, he proposed the simple explanation that smaller creatures get larger in the absence of the predators they had attracted on the mainland and larger creatures become smaller with the absence of food sources.